Properties of expansion-free dynamical stars

Sherif, Abbas; Goswami, Rituparno; Maharaj, S. D.

doi:10.1103/physrevd.100.044039

Cited by 8 publications

(14 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In [21] we considered expansion-free dynamical stars that are non-rotating and non-twisting. It was shown that the existence of such models requires the star to simultaneously accelerate and radiate, in which case the star is necessarily conformally flat.…”

Section: Resultsmentioning

confidence: 99%

“…In the limiting case that g = h = 0 we recover the well known spherically symmetric LRS II class of spacetimes which generalizes spherically symmetric solutions to Einstein field equations (EFEs). These spacetimes with vanishing rotation and spatial twist was employed in [21] to study expansion-free and dynamic stellar models. LRS spacetimes, a generalization of LRS II spacetimes, on the other hand include solutions with nonzero vorticity and nonzero spatial twist.…”

Section: Locally Rotationally Symmetric Spacetimes and Its 1 + 1 + 2 ...mentioning

confidence: 99%

“…In particular, it was shown that the instability is entirely governed by the pressures and the radial profile of the energy density. In a recent work by Sherif et al [21] the authors employed, for the first time, the 1+1+2 formalism (a semitetrad covariant method for anlyzing the field equations) to study the properties of expansion free models. With emphasis on non-rotating and non-twisting stars the authors found that a necessary condition for the existence of such stars is that the star simultaneously accelerate and radiate.…”

Section: Introductionmentioning

confidence: 99%

“…In particular we would like to know the restrictions that the addition of spatial twist or/and rotation induces on the geometric and matter quanties such as acceleration, heat flux, e.t.c. As with our previous work [21], we will make use of the equivalent forms of the field equations from the 1 + 1 + 2 semi-tetrad covariant formulation of general relativity [27][28][29][30][31][32]. The semi-tetrad formalism has proven to be an extremely useful approach in displaying geometrical features in a transparent fashion which are generally very difficult to find using other approaches.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Non-existence of expansion-free dynamical stars with rotation and spatial twist

Sherif,

Goswami,

Maharaj

2020

Preprint

Self Cite

View full text Add to dashboard Cite

Extending a previous work by the same authors, we investigate the existence of expansion-free dynamical stars with non-zero spatial twist and rotation and show that such stars cannot exist. Firstly, it is shown that a rotating expansion-free dynamical star with zero twist cannot exist. This is due to the fact that such stars cannot radiate and they are shear-free, in which case the energy density ρ is time independent. Secondly, we prove that a non-rotating expansion-free dynamical star with non-zero spatial twist also cannot exist, as either the strong energy condition must be violated, i.e. ρ + 3p < 0, or the star must be shear-free in which case the star is static (Θ = Ω = Σ = 0). Finally, if we insist that the rotation and spatial twist are simultaneously non-zero, then the star cannot be shear-free in which case we obtain a quadratic polynomial equation in φ and Σ with no real solutions. Therefore such stars cannot exist.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Locally Rotationally Symmetric Spacetimes and Its 1 + 1 + 2 ...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Non-existence of expansion-free dynamical stars with rotation and spatial twist

Sherif,

Goswami,

Maharaj

2020

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…The final remnants of collapsing object are discussed in the paper. Some other authors have also harnessed this concept in context of charge (see [34][35][36]).…”

Section: Introductionmentioning

confidence: 99%

Charged anisotropic spherical collapse with heat flow

2021

View full text Add to dashboard Cite

In this article, we study the shear-free gravitational collapse of a charged radiating star. The Einstein field equations of gravitational collapse for the charged stars are known to give rise to a high degree of non-linearity in the ordinary differential equation coming from junction conditions. The attempts to solve it analytically proved to be unfortunate. Numerical methods have been suggested in the past. However, the high degree of non-linearity tends to introduce fluctuations and large round off errors in the numerical calculation. A new ansatz is proposed in the present work to reduce the degree of non-linearity. An ordinary differential equation is derived by satisfying junction conditions, and its numerical solution is demonstrated. Physical quantities associated with the collapse process are plotted to observe the effect of charge on these quantities. It is concluded that the charge can delay the collapse of a star and can even prevent it depending upon the amount of charge. It is also verified that the solution satisfies all the energy conditions.

show abstract

Some results on cosmological and astrophysical horizons and trapped surfaces

Sherif

Goswami

Maharaj

2019

Class. Quantum Grav.

View full text Add to dashboard Cite

We study the evolution of horizons of black holes in the 1 + 1 + 2 covariant setting and investigate various properties intrinsic to the geometry of the foliation surfaces of these horizons. This is done by interpreting formulations of various quantities in terms of the geometric and thermodynamic quantities. We establish a causal classification for horizons in different classes of spacetimes. We have also recovered results by Ben-Dov and Senovilla which put cut-offs on the equation of state parameter σ, determining the spacelike, timelike and non-expanding horizons in the the Robertson-Walker class of spacetimes. We show that stability of marginally trapped surfaces (MTS) in the Robertson-Walker spacetimes is only achievable under the conditions of negative pressure, and also classify the spacelike future outer trapping horizons (SFOTH) in the Robertson-Walker spacetimes via bounds on the equation of state parameter σ. For the Lemaitre-Tolman-Bondi (LTB) model, it is shown that a relationship between the energy density and the electric part of the Weyl curvature, E , gives the causal classification of the MOTS. It is further shown that only spacelike MOTS are foliated by stable MTS, and that this stability guarantees no shell crossing. We also provide an explicit proof of the third law of black hole thermodynamics for the LRS II class of spacetimes, and by extension, any spacetime whose outgoing and ingoing null geodesics are normal to the MTS.

show abstract

Properties of expansion-free dynamical stars

Cited by 8 publications

References 39 publications

Non-existence of expansion-free dynamical stars with rotation and spatial twist

Non-existence of expansion-free dynamical stars with rotation and spatial twist

Charged anisotropic spherical collapse with heat flow

Some results on cosmological and astrophysical horizons and trapped surfaces

Contact Info

Product

Resources

About